1. Field of the Invention
The present invention relates to the production of fiber composites with a fiber-reinforced vitreous or glass-ceramic matrix, and more precisely, of composites obtained through winding of preimpregnated fibers and rigidification by heat treatment.
Such materials, developed from fibers of silicon carbide or carbon, for example, are more particularly intended for applications in the aeronautics or space field, which require high temperature resistance, as well as in the field of mechanical stresses.
2. Discussion of Background Information
Two known techniques make it possible to obtain this type of composite.
In a first technique, these composites are produced by cold winding onto a mandrel that is appropriate for preimpregnated fibers, then the wound mandrel is placed into a furnace in order to soften the vitreous or glass-ceramic matrix, after which the material rigidifies during the cooling of the furnace.
This technique does not provide optimal compaction or homogeneity of the composite, because of the cold winding.
In a second technique described in European patent application No. 0 557 140, which was filed in the name of the present assignee, the preimpregnated fibers are deposited onto the mandrel with the aid of a pressure roller in front of which localized heating takes place in order to melt the subjacent vitreous matrix onto which the fibers are pressed.
The disadvantages of this process lie in the impossibility of tightening the fibers during their deposition and in the fact that the composite undergoes, during the entire deposition, a local thermal shock that is detrimental to the quality of the ceramicization of the matrix.
On the other hand, from U.S. Pat. No. 4,976,761, an installation is known that is intended for tension-winding of preimpregnated fibers onto a mandrel disposed inside a furnace. To this end, the pre-heated fibers are delivered at a controlled tension and at a fixed point which faces an opening of the furnace inside which the mandrel is driven in rotation and can be axially displaced.
Even if such an apparatus makes it possible to obtain composites under conditions which assure good compactness and a good ceramicization of the matrix, it is not suitable for winding either elongated pieces or fibers at angles that are substantially less than 90.degree. in relation to the axis of the mandrel.
In fact, since the delivery of the fibers is effected in a manner that is stationary and roughly orthogonal to the axis of the mandrel, it precludes the winding of a mandrel of relatively considerable length, because that would require a furnace of excessive size, since the mandrel must roll from one end to the other in front of the opening through which the fibers enter the furnace. It is completely impossible to wind fibers at angles that are substantially less than 90.degree., since the mandrel can be displaced only axially, that is, orthogonally to the fibers entering the furnace.